1. Technical Field
The present invention relates to a Rankine cycle device, an expansion system and an expansion machine.
2. Description of the Related Art
In a general Rankine cycle device, an expansion machine is operated with a working fluid having a high temperature and a high pressure to generate an electric power with a power extracted from the working fluid by the expansion machine. The working fluid having a high temperature and a high pressure is made by a pump and a heat source such as solar heat, geothermal heat, or exhaust heat.
U.S. Pat. No. 7,418,824 discloses an expansion machine included in a Rankine cycle device. This expansion machine has a structure where a positive displacement expansion mechanism and an electric power generator which is connected to the positive displacement expansion mechanism with a shaft are contained in a sealed container. The expansion machine having such a structure does not require a mechanical seal to prevent the working fluid from leaking to the outside of the sealed container, since the shaft included in the expansion machine does not penetrate the sealed container.
Japanese Patent Application laid-open Publication No. 2009-174494A also discloses a Rankine cycle device 300 using an expansion machine having a similar structure. As shown in FIG. 6, the Rankine cycle device 300 has a pump 301, a heater 302, an expansion machine 303, and a cooler 305. The expansion machine 303 has an expansion mechanism 311, an electric power generator 312 connected to the expansion mechanism 311 with a shaft 313, and a sealed container 310 containing the expansion mechanism 311 and the electric power generator 312. A portion of a flow path leading the working fluid from the outlet of the pump 301 to the inlet of the heater 302 is located in the inside of the sealed container 310 so that the electric power generator 312 is located in the portion of the flow path. For this reason, since a relatively low temperature working fluid flows in or around the electric power generator 312, the electric power generator 312 is cooled by the working fluid.